On visco-elastic modelling of polyethylene terephthalate behaviour during multiaxial elongations slightly over the glass transition temperature

The mechanical response of Polyethylene Terephthalate (PET) in elongation is strongly dependent on temperature, strain and strain rate. Near the glass transition temperature Tg, the stress-strain curve presents a strain softening effect vs strain rate but a strain hardening effect vs strain under conditions of large deformations. The main goal of this work is to propose a viscoelastic model to predict the PET behaviour when subjected to large deformations and to determine the material properties from the experimental data. To represent the non–linear effects, an elastic part depending on the elastic equivalent strain and a non-Newtonian viscous part depending on both viscous equivalent strain rate and cumulated viscous strain are tested. The model parameters can then be accurately obtained trough a comparison with the experimental uniaxial and biaxial tests. The in?uence of the temperature on the viscous part is also modelled and an evaluation of the adiabatic self heating of the specimen is compared to experimental results.

Multiaxial Deformation of Polyethylene and Polyethylene/Clay Nanocomposites: In Situ Synchrotron Small Angle and Wide Angle X-Ray Scattering Study

A unique in situ multiaxial deformation device has been designed and built specifically for simultaneous synchrotron small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) measurements. SAXS and WAXS patterns of high-density polyethylene (HDPE) and HDPE/clay nanocomposites were measured in real time during in situ multiaxial deformation at room temperature and at 55 degrees C. It was observed that the morphological evolution of polyethylene is affected by the existence of clay platelets as well as the deformation temperature and strain rate. Martensitic transformation of orthorhombic into monoclinic crystal phases was observed under strain in HDPE, which is delayed and hindered in the presence of clay nanoplatelets. From the SAXS measurements, it was observed that the thickness of the interlamellar amorphous region increased with increasing strain, which is due to elongation of the amorphous chains. The increase in amorphous layer thickness is slightly higher for the nanocomposites compared to the neat polymer. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 669-677, 2011

A material model for multiaxial stretching and stress relaxation of polypropylene under process conditions

Polypropylene sheets have been stretched at 160 °C to a state of large biaxial strain of extension ratio 3, and the stresses then allowed to relax at constant strain. The state of strain is reached via a path consisting of two sequential planar extensions, the second perpendicular to the first, under plane stress conditions with zero stress acting normal to the sheet. This strain path is highly relevant to solid phase deformation processes such as stretch blow moulding and thermoforming, and also reveals fundamental aspects of the flow rule required in the constitutive behaviour of the material. The rate of decay of stress is rapid, and such as to be highly significant in the modelling of processes that include stages of constant strain. A constitutive equation is developed that includes Eyring processes to model both the stress relaxation and strain rate dependence of the stress. The axial and transverse stresses observed during loading show that the use of a conventional Levy-Mises flow rule is ineffective, and instead a flow rule is used that takes account of the anisotropic state of the material via a power law function of the principal extension ratios. Finally the constitutive model is demonstrated to give quantitatively useful representation of the stresses both in loading and in stress relaxation.

Adaptaci??n espa??ola de la Escala Multiaxial de Afrontamiento Estrat??gico (SACS) de Hobfoll

Resumen tomado de la publicaci??n

Tradução e adaptação da escala de dependência de substâncias do Millon Clinical Multiaxial III para o Brasil

Millon describes the normal personality by means of adaptation styles that are effective in normal environments and personality disorders such as unadapted operating styles. To operacionalize his theoretical model, Millon has built several instruments, including the Millon Clinical Multiaxial Inventory III (MCMI-III), wich consists of a self report inventory composed by 175 true or false response items, containing four verification scales, and others scales wich evaluates 14 personality patterns and 10 clinical syndromes. The Substance Dependence scale (T) is placed along with Clinical Syndromes scales. This research is justified by the lack of a Brazilian instrument to assess personality psychopathological aspects, and aims to translate and semantically adapt the MCMI-III to the Brazilian context, checking validity elements of the Substance Dependence scale, and developing a computer application for assisting the evaluation of assessment results. To this intent, 2.588 individuals data was collected, male and female, aged between 18 and 85 years, characterized as belonging to a clinical or non-clinical group, who took part in the survey via the internet or in person. Respondents completed the MCMI-III, a socio-demographic questionnaire and a subgroup also answered to the Goldberg General Health Questionnaire (GHQ). Besides descriptive statistics, we performed the analysis using the Student t test, principal components analysis and internal consistency. Despite difficulties related to translating very specific English terms, the assessment by judges, experts on Millon´s theory, and the back translation, attested the adequacy of the Brazilian version. Factorial analysis indicated the grouping of translated T scale items into three factors (social activities prejudice, lack of impulse control, and oppositional behavior), by presenting a single item on a fourth factor (apparently related to seeking pleasurable stimuli). The Cronbach alpha for this set of items was 0,82, indicating an acceptable scale reliability. The data analysis resulted in distinction of scores between clinical and non-clinical groups and between men and women; the relationship between high scores on the scale T and the other scales; scores of drug users according to the declared used substance; and the relationship between high scores on T and the verification of disorder or risk on GHQ mental health factor, indicating the instrument´s adequate sensistivity in identifying psychopathologies and the relationship between the different disorders or psychopathological personality patterns. Although further studies are necessary to develop the scores transformation factors, the computerized correction tool was adequate.

Estudos de validade da escala de dependência alcoólica do millon clinical multiaxial inventory iii para o Brasil

This study has as main objectives to translate and to adapt the MCMI-III to brazilian Portuguese, as well as investigate and analyze the involved modifications in the Alcohol Dependence Scale concerning to the results obtained on the validity and on the process of adaptation to Brazil. The inventory was translated and, posteriorly, applied on people with different reading levels to certify that the items are understandable to public in general, from diverse places of the country, divided into clinical and non-clinical groups. Were evaluated 2855 subjects between the ages of 18 and 85 years old, male and female, resident and dwellers of Brazilian cities. The application methods were face-to-face and computerized. Results showed that the clinical group presented significant differences between the means in comparison to the non-clinical group. Through the application of the General Health Questionnaire were developed studies related to the achievement of convergent validity and its results pointed to the relation between the instrument scores and the MCMI-III. The Alcohol Dependence Scale analysis indicated that people who reported abusive use of alcohol had highest scores, indicating adequacy of the instrument on identifying manifestation of disorders and syndromes. Nevertheless, further studies are necessary to the establishment of normative patterns to the Brazilian sample

The therapeutic effects of Millon Clinical Multiaxial Inventory -III assessment feedback

A study was conducted to test the therapeutic effects of assessment feedback on rapport-building and self-enhancement variables (self-verification, self-discovery, self-esteem), as well as symptomatology. Assessment feedback was provided in the form of interpretive information based on the results of the Millon Clinical Multiaxial Inventory-III (MCMI-III). Participants (N = 89) were randomly assigned to three groups: a Feedback group, a Reflective-Counseling group, and a No-Feedback group. The Feedback group was provided with assessment feedback, the Reflective-Counseling group was asked to comment on the meaning of the taking the MCMI-III, the No-Feedback group received general information about the MCMI-III. Results revealed that assessment feedback, when provided in the form of interpretive interpretation positively affects rapport-building and self-enhancement variables (self-verification and self-discovery). No significant results were found in terms of self-esteem or symptom decrease as a function of feedback. However, a significant decrease in symptoms across groups was found. Results indicate that assessment feedback in the form of interpretive information can be used as a starting point in therapy. Implications of the findings are discussed with respect to theory and clinical practice. ^

The therapeutic effects of Millon Clinical Multiaxial Inventory-III assessment feedback

A study was conducted to test the therapeutic effects of assessment feedback on rapport-building and self-enhancement variables (self-verification, self-discovery, self-esteem), as well as symptomatology. Assessment feedback was provided in the form of interpretive information based on the results of the Millon Clinical Multiaxial Inventory- III (MCMI-III). Participants (N = 89) were randomly assigned to three groups: a Feedback group, a Reflective-Counseling group, and a No-Feedback group. The Feedback group was provided with assessment feedback, the Reflective-Counseling group was asked to comment on the meaning of the taking the MCMI-III, the No- Feedback group received general information about the MCMI-III. Results revealed that assessment feedback, when provided in the form of interpretive interpretation positively affects rapport-building and self-enhancement variables (self-verification and self-discovery). No significant results were found in terms of self-esteem or symptom decrease as a function of feedback. However, a significant decrease in symptoms across groups was found. Results indicate that assessment feedback in the form of interpretive information can be used as a starting point in therapy. Implications of the findings are discussed with respect to theory and clinical practice.